全文获取类型
收费全文 | 12082篇 |
免费 | 1601篇 |
国内免费 | 887篇 |
专业分类
电工技术 | 2058篇 |
综合类 | 1308篇 |
化学工业 | 2032篇 |
金属工艺 | 566篇 |
机械仪表 | 690篇 |
建筑科学 | 1194篇 |
矿业工程 | 305篇 |
能源动力 | 842篇 |
轻工业 | 400篇 |
水利工程 | 390篇 |
石油天然气 | 808篇 |
武器工业 | 157篇 |
无线电 | 1085篇 |
一般工业技术 | 1339篇 |
冶金工业 | 405篇 |
原子能技术 | 361篇 |
自动化技术 | 630篇 |
出版年
2024年 | 45篇 |
2023年 | 175篇 |
2022年 | 312篇 |
2021年 | 405篇 |
2020年 | 391篇 |
2019年 | 353篇 |
2018年 | 359篇 |
2017年 | 487篇 |
2016年 | 554篇 |
2015年 | 558篇 |
2014年 | 669篇 |
2013年 | 836篇 |
2012年 | 932篇 |
2011年 | 969篇 |
2010年 | 677篇 |
2009年 | 719篇 |
2008年 | 671篇 |
2007年 | 776篇 |
2006年 | 724篇 |
2005年 | 601篇 |
2004年 | 506篇 |
2003年 | 433篇 |
2002年 | 370篇 |
2001年 | 295篇 |
2000年 | 263篇 |
1999年 | 250篇 |
1998年 | 198篇 |
1997年 | 170篇 |
1996年 | 157篇 |
1995年 | 116篇 |
1994年 | 125篇 |
1993年 | 74篇 |
1992年 | 82篇 |
1991年 | 50篇 |
1990年 | 61篇 |
1989年 | 49篇 |
1988年 | 36篇 |
1987年 | 32篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 13篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 6篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1959年 | 6篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
《Advanced Powder Technology》2022,33(8):103602
To operate a bag filter continuously, pulse-jet cleaning of dust particles from the filter medium is commonly required, and the pulse-jet pressure significantly affects the filter performance. In this study, the accumulation structure of residual dust particles inside and on the surface of a filter medium at different pulse-jet pressures was investigated by constructing a simple model, and the influence of the dust structure on the filter performance was clarified. Using a simple model, we determined the effective ratio of filtration area β, which represents the ratio of the filterable area to the total filtration area, the true resistance coefficient due to the primary dust layer ζp’ thinly deposited on the filter surface, and the true resistance coefficient inside the filter media itself ζf’. The effective ratio of filtration area β decreased with operation time for all pulse-jet pressures; however, it maintained a high value when the pulse-jet pressure was high. The validity of β analyzed by the model was verified using two different methods, and the results showed good agreement, indicating that the model is effective in identifying real conditions. The true resistance coefficient due to the primary dust layer ζp’ decreased as the pulse-jet pressure increased; however, the true resistance coefficient inside the filter media itself ζf’ was the highest at 0.5 MPa. In addition, the dust collection efficiency was different at each pulse-jet pressure, which was considered to be caused by the difference in the dust particle accumulation structure. 相似文献
3.
Rectangular section control technology(RSCT)was introduced to achieve high-precision profile control during silicon steel rolling.The RSCT principle and method were designed,and the whole RSCT control strategy was developed.Specifically,RSCT included roll contour design,rolling technology optimization,and control strategy development,aiming at both hot strip mills(HSMs)and cold strip mills(CSMs).Firstly,through the high-performance variable crown(HVC)work roll optimization design in the upper-stream stands and the limited shifting technology for schedule-free rolling in the downstream stands of HSMs,a hot strip with a stable crown and limited wedge,local spot,and single wave was obtained,which was suitable for cold rolling.Secondly,an approximately rectangular section was obtained by edge varying contact(EVC)work roll contour design,edge-drop setting control,and closed loop control in the upper-stream stands of CSMs.Moreover,complex-mode flatness control was realized by coordinating multiple shape-control methods in the downstream stands of CSMs.In addition,the RSCT approach was applied in several silicon-steel production plants,where an outstanding performance and remarkable economic benefits were observed. 相似文献
4.
Mohammadmahdi Davoudi 《工程优选》2019,51(5):775-795
Although topology optimization is established for linear static problems, more effort is required for solving nonlinear plastic problems. A new topology optimization approach with equivalent static loads (ESLs) is suggested to find the optimum topologies and locations of plastic hinges of thin-walled crash boxes by considering crash-induced deformation, the main crash energy-absorbing mechanism. Together with finite element method crashworthiness analyses, considering all nonlinearities with rate-dependent plasticity, the method was developed using an appropriate time-incremental scheme of ESLs without removing any high values of loads. Analyses show that the crash boxes with optimum topologies have energy-absorbing capabilities equivalent to the original structure. The proposed method is evaluated for two crashes: a crash box at low speed and a double cell subjected to high-speed collision. The results indicate that this method captures nonlinear crushing behaviours and accurate locations of plastic hinges where, if proper reinforcements are made, energy absorption can be enhanced. 相似文献
5.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
6.
Longbang Qing Yuehua Cheng Ru Mu 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(11):2533-2543
Based on theoretical analysis and numerical simulation, the impact of steel fibres on the stress intensity factor (SIF) at the crack tip for cementitious composite was studied. The enhanced toughness of steel fibre reinforced cementitious composite (SFRC) in resisting cracks was explained by the decrement of SIF caused by steel fibre inclusions at the crack tip of the composite. The equivalent initial fracture toughness was used to characterize the crack initiation of SFRC. A simplified method for determining the of SFRC was proposed based on a linear regression method. Fracture tests were conducted on three‐point bending notched beams with different steel fibre volume fractions and specimen sizes to study the crack initiation behaviour of aligned steel fibre reinforced cementitious composite (ASFRC). of ASFRC was calculated, and the size effect of was analysed. The results showed that slightly increased with the steel fibre volume fraction and gradually became stable. For the tested specimens, whose heights varied between 40 and 100 mm, the specimen size had little impact on the . 相似文献
7.
丝网气液分离器分离性能和压力损失分析 总被引:3,自引:0,他引:3
对丝网气液分离器的分离机理进行了详细分析,在此基础上给出了丝网气液分离器的分离效率和压降计算公式。与HG/T 21618-1998《丝网除沫器》中的公式相比,此公式可以用于任意组合的丝网结构,更具普适性,并且能定量分析各种分离机理对分离的贡献。对丝网式空气过滤器计算的结果表明,此公式具有很好的精度,可以用于工程设计。 相似文献
8.
9.
交通平衡分配下的公路桥收费策略 总被引:3,自引:0,他引:3
假定一个城市被一条河流分为两部分(如我国的武汉,重庆等市),河上至少架设了两座公路桥梁,本文研究在交通平衡状态下,怎样制定车辆过桥梁的收费水平,使获得的总收入最大,乘客的总行驶时间最少,对多车种问题,研究了等价的数学模型和算法。还对一个含两座桥梁与三种车型的简单算例,进行了计算与分析。 相似文献
10.